1. Field of the Invention
This invention relates to method and apparatus for annotating electrophotographic prints of photographic negatives using ion projection.
2. Background Art
When used here, the term annotation means any modification of the pictorial image, such as adding a title, frame numbers, or a decorative design; removing part of the image; changing the color or contrast of part of the image; or the like. Several ways have been proposed for annotating electrophotographic prints.
In U.S. Pat. No. 4,774,546, an annotation device includes an illumination source, an addressable light modulation device' and a lens array for forming the modulated light pattern n the photosensitive surface.
In U.S. Pat. No. 4,551,008, an apparatus uses flexible fingers with reflective surfaces to reflect light in order to discharge a photoconductor in a image-wise pattern.
In U.S. Pat. No. 4,752,806, a multi-mode document imaging system capable of copying a document includes an optical system to project light to add another image to the print.
These and other optical methods share the limitation that exposure to light from one of these devices can only reduce the charge on the photoconductor, it cannot increase the amount of charge. The annotation can therefore only be placed in a region in which the photoconductor is substantially undischarged by the exposure through the negative. This is usually accomplished by masking off the area in which the annotation is going to be placed during the exposure to the picture, which retains the charge in the corresponding area on the photoconductor. An optical system is then used to discharge the photoconductor in this region in a pattern that produces the desired annotation. This process results in a box that contains the annotation but is otherwise blank.
This disadvantage can be overcome by using an ion projection device to modify the electrostatic image rather than an optical system. The ion projection device deposits ions onto the photoconductor in an image-wise pattern and by choosing the polarity of the ions, it can either increase or decrease the charge in the image.
The use of an ion projection device to produce black and white annotations by an eletrophotographic printer is described in the IBM Technical Disclosure Bulletin, Vol. 22, No. 12, May 1980, pages 5270-5271.
In U.S. Pat. No. 4,761,669, there is shown an eletrophotographic printing machine in which a first image is recorded on a photoconductive member and developed with a liquid developer of a first color. Thereafter, the first electrostatic image is neutralized. An ion projection device records a second electrostatic image on the photoconductor, and the second image is developed with liquid developer of a second color to form a composite image. The composite image is then transferred to a receiver sheet.
None of these references disclose optical or ion projection means for annotation which choose the position, color, or density of the annotation in response to the content of the pictorial image.
In U.S. Pat. No. 4,268,164, an electrophotographic apparatus copies and annotates documents. The apparatus includes a copy board on which the document to be copied is placed and slidable position indicating means along the edge of the copy board that can be adjusted to indicate where the annotation should be placed relative to the image of the document. This, however, is a manually operated apparatus in which an operator must position the indicating means. Also, the system requires that the first image end or be masked off in the region where the second image or annotation is to be placed. It does not provide for superimposing the annotation on the image of the document.